1. Field of the Invention
The present invention relates to an engine control device installed in a vehicle, and more particularly to a crank angle detecting device for an internal combustion engine.
2. Description of the Related Art
A crank angle position detecting means and a cam signal detecting means are used in order to perform engine crank angle position control and cylinder identification. The crank angle position detecting means is generally one that provides a signal every 10° CA (crank angle) in order to perform angle control with excellent accuracy. In addition, devices that perform early stage cylinder identification in order to improve startability have been proposed, and for the case of a four-cylinder engine, cylinder identification is performed at one ignition stroke interval (180° CA).
A device disclosed in Japanese Patent Laid-Open No. 11-315748, for example, is a conventional internal combustion engine crank angle detecting device.
The crank angle position detecting means in the device uses a 10° CA signal, and crank angle reference positions (missing teeth) are established in two locations, every 180° CA, in one crank revolution (360° CA period).
Further, identification signals for from one to four cylinders are established every 180° CA in two crank rotations (720° CA period) as cam signals.
Crank angle locations are detected by the above-mentioned crank angle detecting means, and cylinder identification is performed with respect to the number of cylinder identification signals in a 180° CA period of the cam signal. The number of cylinder identification signals in the 180° CA period of the cam signal is different for each of the cylinders, and therefore it becomes possible to identify the cylinders every ignition stroke interval. In addition, such a structure is capable of cylinder identification even if the cam phase changes due to a VVT (variable valve timing mechanism).
For cases in which a different number of cylinder identification signals are established for each cylinder in the cam signal of an engine with VVT, it is necessary to establish cylinder identification signals equal to the number of cylinders during a relatively small angular gap so as to achieve cylinder identification, even if the cam shaft angle changes by VVT, with a conventional device as discussed above. The gap between signals becomes small if the diameter of a cam signal vane is small, and therefore there is a problem in that the cylinder identification signal cannot be detected by the cam signal detecting means.
Further, the number of cylinder identification signals of the cam signal increases if there are additional cylinders, so that the signal gap becomes increasingly short, and there is a problem in that detection of the cylinder identification signal cannot be made by the cam signal detecting means.